Method for calculating theoretical power of a wind farm based on extrapolation of anemometer tower data

Abstract

A method of calculating theoretical power of wind farm based on extrapolation of anemometer tower data includes following steps. A number of anemometer towers in a wind farm is selected, and analyzing historical data acquired by the number of anemometer towers. An air density is calculated based on the historical data of the number of anemometer towers. A power curve is calibrated based on the historical data of the number of anemometer towers. The power curve is fit based on a wind speed and a wind power of a fan head of each wind turbine based on the historical data. An theoretical power calculation extrapolation model of anemometer tower data is constructed. Real-time anemometer tower wind data and a calibrated air density are inputted into the theoretical power calculation model and calculating the wind power. The theoretical power is obtained.

What is claimed is: 
     
         1 . A method of calculating theoretical power of wind farm based on extrapolation of anemometer tower data, the method comprising:
 selecting a plurality of anemometer towers in a wind farm, and analyzing historical data acquired by the plurality of anemometer towers;   calculating an air density based on the historical data of the plurality of anemometer towers;   calibrating a power curve based on the historical data of the plurality of anemometer towers;   fitting the power curve based on a wind speed and a wind power of a fan head of each wind turbine based on the historical data;   constructing a theoretical power calculation extrapolation model of anemometer tower data by extrapolating the wind speed of each of the plurality of anemometer towers to a height of each hub of the wind turbine;   inputting real-time anemometer tower wind data and a calibrated air density into the theoretical power calculation model and calculating the wind power; and   obtaining the theoretical power by analyzing the extrapolated wind speed at the height of hub and the wind speed of the fan head of each wind turbine.   
     
     
         2 . The method of  claim 1 , wherein the air density is calculated according to the historical data as follows: 
       
         
           
             
               
                 
                   ρ 
                   i 
                 
                 = 
                 
                   
                     B 
                     i 
                   
                   
                     RT 
                     i 
                   
                 
               
               , 
               
                 
 
               
                
               
                 
                   
                     ρ 
                     _ 
                   
                   = 
                   
                     
                       1 
                       N 
                     
                      
                     
                       
                         ∑ 
                         
                           i 
                           = 
                           1 
                         
                         N 
                       
                        
                       
                         ρ 
                         i 
                       
                     
                   
                 
                 ; 
               
             
           
         
         wherein ρ i  is the instantaneous average air density, B i  is the instantaneous pressure, R is the gas constant 287.05 (J/kg·K). T i  is the average temperature, N is the number of samples,  ρ  is the average air density. 
       
     
     
         3 . The method of  claim 1 , wherein the power curve is calibrated as follows:
 while the air density ranges within 1.225 kg/m 3 ±0.05 kg/m 3 , the power curve does not need to be calibrated; otherwise the power curve is calibrated as follows:   for the wind turbine with stall control, constant collective pitch, and constant speed, the power curve is calibrated by following formula:   
       
         
           
             
               
                 
                   P 
                   correct 
                 
                 = 
                 
                   
                     P 
                     0 
                   
                   · 
                   
                     
                       ρ 
                       _ 
                     
                     
                       ρ 
                       0 
                     
                   
                 
               
               ; 
             
           
         
         for the wind turbine with automatic power control, the power curve is calibrated by following formula: 
       
       
         
           
             
               
                 
                   V 
                   correct 
                 
                 = 
                 
                   
                     
                       V 
                       0 
                     
                     ( 
                     
                       
                         ρ 
                         0 
                       
                       
                         ρ 
                         _ 
                       
                     
                     ) 
                   
                   
                     1 
                     / 
                     3 
                   
                 
               
               ; 
             
           
         
         wherein P correct  is the calibrated wind power; P 0  is the wind power according to theoretical power curve; ρ 0  is the standard air density; V 0  is the original wind speed; V correct  is the wind speed after the correction;  ρ  is the measured average density. 
       
     
     
         4 . The method of  claim 3 , wherein the power curve is fit according to the wind speed and the wind power of the fan head as follows:
 the power curve is fit according to method of bins; the wind speed is divided with a bin width of 0.5 m/s, and the wind power according to each bin is obtained through:   
       
         
           
             
               
                 
                   P 
                   i 
                 
                 = 
                 
                   
                     1 
                     
                       N 
                       i 
                     
                   
                    
                   
                     
                       ∑ 
                       
                         j 
                         = 
                         1 
                       
                       
                         N 
                         i 
                       
                     
                      
                     
                       P 
                       
                         i 
                         , 
                         j 
                       
                     
                   
                 
               
               ; 
             
           
         
         
           
             
               
                 
                   V 
                   i 
                 
                 = 
                 
                   
                     1 
                     
                       N 
                       i 
                     
                   
                    
                   
                     
                       ∑ 
                       
                         j 
                         = 
                         1 
                       
                       
                         N 
                         i 
                       
                     
                      
                     
                       V 
                       
                         i 
                         , 
                         j 
                       
                     
                   
                 
               
               ; 
             
           
         
         wherein P i  is the mean power value of the i-th bin, P i,j  is power value in j data group of the i-th bin, V i  is the average value of the wind speed of the i-th bin, V i,j  is the wind speed in j data group of the i-th bin, N i  is the quantity of the data in the i-th bin. 
       
     
     
         5 . The method of  claim 4 , wherein the theoretical power calculation model is constructed as follows:
 considering an effect to the airflow field caused by terrain, roughness changes, wake effects of wind turbine, and performance of wind turbine, and constructing a mapping relationship between the wind speed, the wind direction, and the output power of wind farm by combining wind farm layout;   constructing wind speed conversion function of each wind direction sector by extrapolating the wind speed of each of the plurality of anemometer towers to a height of each hub of wind turbine via adopting micro meteorology theory or fluid dynamics computation method:
     V   extrapolation =ƒ( V   anemometer tower   , k   1   , k   2   , . . . , k   n );
 
   wherein V extrapolation  is the wind speed while extrapolating the wind speed of each of the plurality of anemometer towers to a height of each hub of wind turbine; V anemometer tower  is the measured real-time wind speed of anemometer tower; k 1 , k 2 , . . . , k n  are impact factors, ƒ is the conversion function;   constructing regression equation by adopting historical extrapolating wind speed and wind speed of fan head, and correcting the historical extrapolating wind speed;   computing theoretical power of each wind turbine by fitting the power curve according to the third step and the fourth step based on corrected historical extrapolating wind speed; and   obtaining the theoretical power of wind farm by accumulating the theoretical power of each wind turbine in the wind farm.